AsyncIO is the current state of the art in Python concurrent programming. It combines the concept of futures and an event loop with the coroutines we discussed in Chapter 9, The Iterator Pattern. The result is about as elegant and easy to understand as it is possible to get when writing concurrent code, though that isn't saying a lot!
AsyncIO can be used for a few different concurrent tasks, but it was specifically designed for network I/O. Most networking applications, especially on the server side, spend a lot of time waiting for data to come in from the network. This can be solved by handling each client in a separate thread, but threads use up memory and other resources. AsyncIO uses coroutines as a sort of lightweight thread.
The library provides its own event loop, obviating the need for the several lines long the while loop in the previous example. However...